Radius (bone)
Encyclopedia
The radius is one of the two large bone
s of the forearm
, the other being the ulna
. It extends from the lateral
side of the elbow to the thumb
side of the wrist
and runs parallel to the ulna, which exceeds it in length and size. It is a long bone, prism
-shaped and slightly curved longitudinally. The radius articulates with the capitulum of the humerus
, the radial notch
and the head of the ulna. The corresponding bone in the lower leg
is the tibia
.
The word radius is Latin for "ray". In the context of the radius bone, a ray can be thought of rotating around an axis line extending diagonally from center of capitulum
to the center of distal ulna
. While the ulna
is the major contributor to the elbow joint, the radius primarily contributes to the wrist
joint.
consists of a somewhat cylindrical head articulating with the ulna and the humerus, a neck, and a double tuberosity. The body of the radius
is self-explanatory, and the lower extremity of the radius
is roughly quadrilateral in shape, with articular surfaces for the ulna
, scaphoid and lunate bone
s. The distal end of the radius forms a palpable point called the styloid process
. Along with the proximal
and distal radioulnar articulation
s, an interosseous membrane originates medially along the length of the body of the radius to attach the radius to the ulna.
muscle inserts on the radial tuberosity of the upper extremity of the bone. Sometimes it may break.
The upper third of the body of the bone attaches to the supinator
, the flexor digitorum superficialis, and the flexor pollicis longus muscles.
The middle third of the body attaches to the extensor ossis metacarpi pollicis, extensor primi internodii pollicis, and the pronator teres muscles.
The lower quarter of the body attaches to the pronator quadratus
muscle and the tendon
of the supinator longus.
is enclosed in a strong wall of compact bone. It is thickest along the interosseous border and thinnest at the extremities, save over the cup-shaped articular surface (fovea) of the head.
The trabeculae of the spongy tissue are somewhat arched at the upper end and pass upward from the compact layer of the shaft to the fovea capituli (the humerus
's cup-shaped articulatory notch); they are crossed by others parallel to the surface of the fovea. The arrangement at the lower end is somewhat similar. It is missing in radial aplasia
.
types of the radius include:
s) and reduced or modified in animals with flippers or vestigial forelimbs.
See also=
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
s of the forearm
Forearm
-See also:*Forearm flexors*Forearm muscles...
, the other being the ulna
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...
. It extends from the lateral
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
side of the elbow to the thumb
Thumb
The thumb is the first digit of the hand. When a person is standing in the medical anatomical position , the thumb is the lateral-most digit...
side of the wrist
Wrist
In human anatomy, the wrist is variously defined as 1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand;...
and runs parallel to the ulna, which exceeds it in length and size. It is a long bone, prism
Prism (geometry)
In geometry, a prism is a polyhedron with an n-sided polygonal base, a translated copy , and n other faces joining corresponding sides of the two bases. All cross-sections parallel to the base faces are the same. Prisms are named for their base, so a prism with a pentagonal base is called a...
-shaped and slightly curved longitudinally. The radius articulates with the capitulum of the humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
, the radial notch
Radial notch
The radial notch of the ulna is a narrow, oblong, articular depression on the lateral side of the coronoid process; it receives the circumferential articular surface of the head of the radius....
and the head of the ulna. The corresponding bone in the lower leg
Human leg
The human leg is the entire lower extremity or limb of the human body, including the foot, thigh and even the hip or gluteal region; however, the precise definition in human anatomy refers only to the section of the lower limb extending from the knee to the ankle.Legs are used for standing,...
is the tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
.
The word radius is Latin for "ray". In the context of the radius bone, a ray can be thought of rotating around an axis line extending diagonally from center of capitulum
Capitulum of the humerus
In human anatomy of the arm, the lateral portion of the articular surface of the humerus consists of a smooth, rounded eminence, named the capitulum of the humerus....
to the center of distal ulna
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...
. While the ulna
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...
is the major contributor to the elbow joint, the radius primarily contributes to the wrist
Wrist
In human anatomy, the wrist is variously defined as 1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand;...
joint.
Shape
The radius has a body and two extremities. The upper extremity of the radiusUpper extremity of radius
The upper extremity of the radius presents a head, neck, and tuberosity.* The radial head has a cylindrical form, and on its upper surface is a shallow cup or fovea for articulation with the capitulum of the humerus...
consists of a somewhat cylindrical head articulating with the ulna and the humerus, a neck, and a double tuberosity. The body of the radius
Body of radius
The body of the radius is prismoid in form, narrower above than below, and slightly curved, so as to be convex lateralward...
is self-explanatory, and the lower extremity of the radius
Lower extremity of radius
-Articular surfaces:It is provided with two articular surfaces - one below, for the carpus, and another at the medial side, for the ulna.* The carpal articular surface is triangular, concave, smooth, and divided by a slight antero-posterior ridge into two parts...
is roughly quadrilateral in shape, with articular surfaces for the ulna
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...
, scaphoid and lunate bone
Lunate bone
The lunate bone is a carpal bone in the human hand that may be distinguished by its deep concavity and crescentic outline. It is situated in the center of the proximal row of the carpus region between the fore arm and hand...
s. The distal end of the radius forms a palpable point called the styloid process
Radial styloid process
The radial styloid process is a projection of bone on the lateral surface of the distal radius bone. It extends obliquely downward into a strong, conical projection. The tendon of the brachioradialis attaches at its base, and the radial collateral ligament of the wrist attaches at its apex...
. Along with the proximal
Proximal radioulnar articulation
The proximal radioulnar articulation is a trochoid or pivot joint between the circumference of the head of the radius and the ring formed by the radial notch of the ulna and the annular ligament.-See also:...
and distal radioulnar articulation
Distal radioulnar articulation
The distal radioulnar articulation is a pivot-joint formed between the head of the ulna and the ulnar notch on the distal radius.-Ligaments:The articular surfaces are connected together by the following ligaments:...
s, an interosseous membrane originates medially along the length of the body of the radius to attach the radius to the ulna.
Muscle attachments
The bicepsBiceps
Biceps may refer to:*Biceps brachii muscle, a muscle located on the inside of the upper arm*Biceps femoris muscle, one of the hamstring muscles of the back of each thigh*Biceps , a point in a metrical pattern...
muscle inserts on the radial tuberosity of the upper extremity of the bone. Sometimes it may break.
The upper third of the body of the bone attaches to the supinator
Supinator muscle
In human anatomy, the supinator is a broad muscle in the posterior compartment of the forearm, curved around the upper third of the radius. Its function is to supinate the forearm.-Terminology:...
, the flexor digitorum superficialis, and the flexor pollicis longus muscles.
The middle third of the body attaches to the extensor ossis metacarpi pollicis, extensor primi internodii pollicis, and the pronator teres muscles.
The lower quarter of the body attaches to the pronator quadratus
Pronator quadratus
Pronator quadratus is a square shaped muscle on the distal forearm that acts to pronate the hand.As it is on the anterior side of the arm, it is innervated by a branch of the median nerve, the anterior interosseous nerve...
muscle and the tendon
Tendon
A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other...
of the supinator longus.
Structure
The long narrow medullary cavityMedullary cavity
The medullary cavity is the central cavity of bone shafts where red bone marrow and/or yellow bone marrow is stored; hence, the medullary cavity is also known as the marrow cavity...
is enclosed in a strong wall of compact bone. It is thickest along the interosseous border and thinnest at the extremities, save over the cup-shaped articular surface (fovea) of the head.
The trabeculae of the spongy tissue are somewhat arched at the upper end and pass upward from the compact layer of the shaft to the fovea capituli (the humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
's cup-shaped articulatory notch); they are crossed by others parallel to the surface of the fovea. The arrangement at the lower end is somewhat similar. It is missing in radial aplasia
Radial aplasia
Radial aplasia is a congenital defect which affects the formation of the radius bone in the arm. The radius is the lateral bone which connects to the wrist via articulation with the carpal bones. A child born with this condition has either a short or absent radius bone in one or both of his or her...
.
Fracture
Specific fractureBone fracture
A bone fracture is a medical condition in which there is a break in the continuity of the bone...
types of the radius include:
- Essex-Lopresti fractureEssex-Lopresti fractureThe Essex-Lopresti fracture is a fracture of the radial head with concomitant dislocation of the distal radio-ulnar joint with disruption of the interosseous membrane...
- a fracture of the radial headHead of radiusThe head of the radius has a cylindrical form, and on its upper surface is a shallow cup or fovea for articulation with the capitulum of the humerus....
with concomitant dislocation of the distal radio-ulnar jointDistal radioulnar articulationThe distal radioulnar articulation is a pivot-joint formed between the head of the ulna and the ulnar notch on the distal radius.-Ligaments:The articular surfaces are connected together by the following ligaments:...
with disruption of the interosseous membraneInterosseous membrane of the forearmThe interosseous membrane of the forearm is a fibrous sheet that connects the radius and the ulna...
. - Distal radius fractureDistal radius fractureA distal radius fracture is a common bone fracture of the radius in the forearm. Because of its proximity to the wrist joint, this injury is often called a wrist fracture...
- Galeazzi fractureGaleazzi fracture-External links:* - gentili.net* - learningradiology.com...
- a fracture of the radius with dislocation of the distal radioulnar joint - Colles' fractureColles' fractureA Colles' fracture, also Colles fracture, is a fracture of the distal radius in the forearm with dorsal displacement of the wrist and hand. The fracture is sometimes referred to as a "dinner fork" or "bayonet" deformity due to the shape of the resultant forearm...
- a distal fracture of the radius with dorsal (posterior) displacement of the wrist and hand - Smith's fractureSmith's fractureA Smith's fracture, also sometimes known as a reverse Colles' fracture is a fracture of the distal radius. It is caused by a direct blow to the dorsal forearm or falling onto flexed wrists, as opposed to a Colles' fracture which occurs as a result of falling onto wrists in extension...
- a distal fracture of the radius with volar (ventral) displacement of the wrist and hand - Barton's fractureBarton's fractureA Barton's fracture is an intra-articular fracture of the distal radius with dislocation of the radiocarpal joint.There exist two types of Barton's fracture - dorsal and palmar, the latter being more common. The Barton's fracture is caused by a fall on an extended and pronated wrist increasing...
- an intra-articular fracture of the distal radius with dislocation of the radiocarpal joint.
- Galeazzi fracture
In other animals
In four-legged animals, the radius is the main load-bearing bone of the lower forelimb. Its structure is similar in most terrestrial tetrapods, but it may be fused with the ulna in some mammals (such as horseHorse
The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...
s) and reduced or modified in animals with flippers or vestigial forelimbs.
See also=
- Bone terminology
- Terms for anatomical location
- Ossification of radiusOssification of radiusThe radius is one of the two bones in the forearm.The radius is ossified from three centers: one for the body, and one for either extremity...